Dressing mechanism

ABSTRACT

A device for dressing an arcuate surface on a grinding wheel wherein a diamond tool is rotated about an axis on a transversely pivoted platen to form the arc and adjusting screw means extends along the axis to transversely pivot the tool in order to adjust the distance of the tool from the first axis.

United States Patent 72] Inventors Herbert R. Uhtenwoldt;

Donald R. Johnson, both of Worcester, Mass.

June 25, 1969 Sept. 28, 1971 The lleald Machine Company Worcester, Mass.

[2 i 1 Appl. No. [22] Filed [45] Patented [73] Assignee [54] DRESSING MECHANISM 3 Claims, 2 Drawing Figs.

11.8. CI 125/11 A B24b 53/06 Field Search 125/11 56] References Cited UNITED STATES PATENTS 2,336,650 12/1943 Storz 125/11 2,642,059 6/1953 Muench 125/11 1,826,219 10/1931 Parker 125/11 Primary Examiner-Harold D. Whitehead Attorney-Norman S. Blodgett ABSTRACT: A device for dressing an arcuate surface on a grinding wheel wherein a diamond tool is rotated about an axis on a transversely pivoted platen to form the arc and adjusting screw means extends along the axis to transversely pivot the tool in order to adjust the distance of the tool from the first axis.

PATENTED isms m FIG.|

FIG, 2

INVENTORS HERBERT R. UHTENWOLDT BY DONALD R. JOHNSON mxW ATTORNEY nnsssmc MECHANISM BACKGROUND OF THE INVENTION In the grinding of annular grooves as, for instance, the grooves of a ball bearing race, it is common practice to use a so-called radius dresser for dressing the working surface of the abrasive wheel. It is important that this surface be properly dressed because such grooves are generally ground by the socalled plunge into the work without reciprocation along the axis of the wheel. The final shape and quality of the groove,.therefore, depends on the accuracy with which the wheel is dressed. In the past, the difficulty has been experienced with a radius dressing mechanism that it is hard to adjust the radius of curvature through which the diamond is moved. Although means of adjustment have usually been provided using reeds and other fiexures, this has been a somewhat inaccurate and crude operation involving a certain amount of trial and error. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a dressing mechanism for producing a working surface on an abrasive wheel, which surface is smooth and geometrically accurate.

Another object of this invention is the provision of a dressing mechanism for producing an annular surface on an abrasive wheel with high accuracy of geometry.

A further object of the present invention is the provision of a dressing mechanism for radius dressing, wherein the radius is capable of fine adjustment without difficulty, while retaining substantial rigidity.

It is another object of the instant invention to provide a radius dresser, wherein the diamond is supported in such a manner as to permit a minimum of vibration by virtue of the incorporation of damping mechanisms.

SUMMARY OF THE INVENTION In general, the invention consists of a dressing mechanism for a grinding machine, having a housing, a primary platen mounted on the housing for rotation about a first axis, and a secondary platen mounted on the primary platen for hinged motion about a second axis perpendicular to and spaced from the first axis. A diamond bracket is mounted on the secondary platen and has a leg which extends parallel to and spaced from the first axis and which carries a diamond extending from a surface facing toward the first axis. An adjusting shaft extends between the housing and the secondary platen to rotate it about the secondary axis to adjust the distance that the diamond lies from the first axis.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a vertical sectional view of a portion of a dressing mechanism incorporating the principles of the present invention, and

FIG. 2 is a front elevation of a portion of the apparatus taken on the line II-II of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, it can be seen that the dressing mechanism, indicated generally by the reference numeral 10, is shown in use with an abrasive wheel 11 mounted on a horizontal axis 12. The dressing mechanism is of the general type shown and described in the patent application of Herbert R. Uhtenwoldt, Ser. No. 800,815, filed Feb. 6,1969 now US.

method, wherein the wheel is fed directly Pat. No. 3,490,432. The wheel 11 is provided with an annular working surface, and it is the function of the dressing mechanism to renew this surface from time to time.

The dressing mechanism has a housing 12 and rotatably mounted on this housing at the lower portion thereof is a primary platen 13 which is mounted on the housing for rotation about a first axis AA which passes through the center of the shaft 12 and is tangential to the minor axis of the annular surface of the abrasive wheel 11 which is to be dressed. A secondary platen 14 is mounted on the primary platen for hinged motion about a second axis defined by a hinge pin 15, which axis is perpendicular to and spaced laterally from the first axis AA. A diamond bracket 16 is mounted on the secondary platen 14 and is provided with a leg 17 which extends vertically parallel to and spaced from the first axis and carries a diamond 18 which extends from a surface 19 of the leg which faces toward the first axis.

An adjusting shaft 21 extends vertically through the housing 12, through the platen 13, into the platen M. It acts on the secondary platen 14 in such a way as to rotate it about the secondary axis and the hinge pin 15 to adjust the distance of the diamond 18 from the first axis AA. The adjusting shaft is provided with 2 longitudinally spaced threaded portions 22 and 23 which have slightly different pitch. These portionsengage corresponding threads formed in the primary and secondary platens, respectively, to form a differential screw mechanism.

The shaft 21 and the threads are concentric with the first axis AA, and the shaft is provided with a neck or portion 24 of small diameter lying between the threaded portions 22 and 23 to accommodate a degree of misalignment by bending. This misalignment takes place when the platens are movedto various positions of relative angularity as the position of the diamond 18 is adjusted.

A prestressed resilient seal, such as a plastic tube 25, lies between opposed surfaces of the platens 13 and 14 about a substantial portion of their peripheries. The seal is selected to be of such a size that it remains under stress at advanced angular positions of the platens in order to provide a closure and a damping function. As is evident in the drawing, the seal is wedged in a triangular passage between a vertical outer periphery of the lower platen 14, an inclined inner surface of the primary platen l3, and a metal plate 26 which underlies the inclined surface of the primary platen.

The bracket 16 is mounted on the platen 14 by the junction of a tongue 27 and a groove 28. In addition, a permanentconnection is brought about by use of bolts 29 operating in elongated apertures in the upper portion of the bracket 16. A bellville spring 31 is located between the two platens at a position spaced away from the hinge pin 15 to keep the platens under spring tension toward separation. This serves to take up any backlash in the threads 22 and 23 as they cooperate with the corresponding threaded portions of the platens l3 and 14, respectively.

The upper end of the shaft 21 emerges from the housing 12 and is provided with a knob 32 by which it can be rotated for adjustment of the diamond. The knob is provided with suitable calibrated markings to assist in the adjustment. The platen 13 is mounted on the lower end of a vertical shaft 33 which is mounted in suitable hearings in the housing 12 independently of the shaft 21. The center of the shaft 33 is provided with a gear 34 which is engaged by a rack 35 which, in turn, is actuated in the usual way by hydraulic cylinders. The rack can be adjusted by means of a threaded mechanism 36 which is mounted in the housing 12 and operates on the rack. This determines the length of the are through which the diamond is moved during a dressing operation.

The operation of the invention will now be readily understood, in view of the above description. The diamond dressing mechanism has a fine adjustment which uses a plain bearing pivot associated with the hinge pin 15. It makes use of the differential screw mechanism incorporated in the shaft 21 with its threads 22 and 23 of slightly different pitch. By this means, a very rigid construction is provided, particularly compared with dressing mechanisms using reed-type adjustments. Any backlash in the pivot around the hinge pin and in the threads 22 and 23 is taken up by the bellville spring 31. An elastomer bushing 37 also lies between the platens l3 and 14 to provide damping against induced vibrations. A plastic tube 25 provides viscoelastic damping and sealing. Since the diamond bracket 16 swings through an are around the hinge pin 15, the shaft 21 has to bend between the screws 22 and 23 and, for that reason, the reduced portion 24 is provided. Since this neck is relatively short, the required axial rigidity is still maintained. Gradations which are one-eighth inch apart are provided on the knob 32, and this is equivalent to 0.0001 inch in motion of the diamond normal to the grinding wheel axis. This means that there is over 1,000-to-1 amplification, and this amplification is free of hysteresis. For a coarse adjustment, of course, the bracket 16 is loosened by unscrewing the bolts 29; it is then moved along the track formed by the tongue 27 and the groove 28.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

l. A dressing mechanism for a grinding machine, comprismg a. a housing,

b. a primary platen mounted on the housing for rotation about a first axis,

c. a secondary platen mounted on the primary platen for hinged motion about a second axis perpendicular to the first axis,

d. a diamond bracket mounted on the secondary platen and having a leg which extends parallel to and spaced from the first axis and carries a diamond extending from a surface facing toward the first axis, and

e. an adjusting shaft extending between the housing and the secondary platen to rotate it about the secondary axis to adjust the distance of the diamond from the first axis, the adjusting shaft being provided with two longitudinally spaced threaded portions of slightly different pitch, which portions engage corresponding threads formed in the primary and secondary platens, respectively, the shaft and the threads being concentric with the first axis, and the shaft being provided with a portion of small diameter between the threaded portions to accommodate a degree of misalignment that takes place when the platens are moved to substantial angularity as the position of the diamond is adjusted.

2. A dressing mechanism as recited in claim 1, wherein a prestressed resilient seal lies between opposed surfaces of the platens about a substantial portion of their periphery, the seal remaining under stress even at advanced angular positions of the platens to provide a closure and a damping function.

3. A dressing mechanism for a grinding machine, comprising a. a housing,

b. a rotation shaft mounted on the housing for rotation about its axis and extending at one end from the housing,

c. a primary platen mounted on the said one end of the shaft,

d. a secondary platen mounted on the primary platen for hinged motion about a second axis perpendicular to the shaft axis,

e. a diamond bracket mounted on the secondary platen and having a leg which extends parallel to and spaced from the shaft axis and which carries a diamond extending from a surface facing toward the shaft axis, and

e. an adjusting shaft extending through a coaxial bore through the shaft to rotate the secondar platen about the second axis to ad ust the dlstance of t e diamond from the first axis. 

1. A dressing mechanism for a grinding machine, comprising a. a housing, b. a primary platen mounted on the housing for rotation about a first axis, c. a secondary platen mounted on the primary platen for hinged motion about a second axis perpendicular to the first axis, d. a diamond bracket mounted on the secondary platen and having a leg which extends parallel to and spaced from the first axis and carries a diamond extending from a surface facing toward the first axis, and e. an adjusting shaft extending between the housing and the secondary platen to rotate it about the secondary axis to adjust the distance of the diamond from the first axis, the adjusting shaft being provided with two longitudinally spaced threaded portions of slightly different pitch, which portions engage corresponding threads formed in the primary and secondary platens, respectively, the shaft and the threads being concentric with the first axis, and the shaft being provided with a portion of small diameter between the threaded portions to accommodate a degree of misalignment that takes place when the platens are moved to substantial angularity as the position of the diamond is adjusted.
 2. A dressing mechanism as recited in claim 1, wherein a prestressed resilient seal lies between opposed surfaces of the platens about a substantial portion of their periphery, the seal remaining under stress even at advanced angular positions of the platens to provide a closure and a damping function.
 3. A dressing mechanism for a grinding machine, comprising a. a housing, b. a rotation shaft mounted on the housing for rotation about its axis and extending at one end from the housing, c. a primary platen mounted on the said one end of the shaft, d. a secondary platen mounted on the primary platen for hinged motion about a second axis perpendicular to the shaft axis, d. a diamond bracket mounted on the secondary platen and having a leg which extends parallel to and spaced from the shaft axis and which carries a diamond extending from a surface facing toward the shaft axis, and e. an adjusting shaft extending through a coaxial bore through the shaft to rotate the secondary platen about the second axis to adjust the distance of the diamond from the first axis. 